Processing units execute instructions to read, manipulate, and write data. Both the instructions and data are commonly stored in a separate memory, which is coupled to the processing unit via a communication channel, or memory channel. In a common example, a typical personal computer includes a central processing unit (CPU), a quantity of dynamic, random-access memory (DRAM), and a memory controller IC that manages the flow of information between the CPU and DRAM.
DRAMs store information in arrays of memory cells arranged in rows and columns. Memory cells are commonly accessed (connected to sense amplifiers) one row at a time, in which case a row is often termed a “page.” The number of memory cells per unit area, termed memory density, grows with process improvements in DRAM fabrication. Such density improvements reduce the price of storage, but also increase the number of memory cells in a given page. If a page provides access to the contents of more memory cells than can be used by the processing unit requesting the access, then the power used to access the unneeded information is wasted.